The natural predators of the koala include dingoes, owls, eagles and pythons. However, according to the Australian Koala Foundation, these predators have little impact on wild populations, even though they prey on juvenile koalas.
When the Europeans settled in Australia, they bought dogs and cats. In this environment, large feral cats also feed on young koalas. When the mother climbs down a tree to change to another, the cat ascends to prey on her young.
The greatest danger to koalas is not from other animals that prey on them for food but from humans. Koala habitat is lost when man clears eucalyptus for homes and fields. As humans settle near the habitat of the koala, the animals experience increased disturbance. Domesticated animals living with humans cause injury or death local koalas. Automobiles present another danger when koalas cross roads. The pesticides used on lawns and gardens transfer to waterways, affecting the health of the koala. As the available habitat diminishes, the competition for food and territory increases due to overcrowding. The animals experience increased stress, which increases their susceptibility to disease, especially due to the chlamydia organism that leads to four serious diseases in koala bears. Additionally, brushfires, often from human sources, have the ability to wipe out an entire colony of koalas in a short time.